Accuracy of In-Situ Water-to-Cement Meters for Concrete

Concrete’s water to cementitious (w/cm) ratio is the most important indicator of the overall strength and durability of the structure. A method to determine the w/cm ratio on-site is important and needed for quality assurance and quality control. There are currently limited standardized techniques for the measurement of w/cm on-site and those techniques can be very time consuming. A developed in-situ microwave moisture meter exists that relies on the difference in the dielectric constant of concrete from that of water to estimate the w/cm ratio. In this report, the accuracy and precision of the meter is studied. Several paste, mortar, and concrete mixes with known w/cm ratios as well as aggregates with known moisture contents were measured with the Cementometerᵀᴹ device. An AASHTO T318-02 microwave test was also performed in comparison to the Cementometerᵀᴹ on known w/cm values. Statistical methods included a t-test determining the accuracy of the device.For precision, linear regression analysis, absolute difference, and sum of squared error calculations were made between the Cementometerᵀᴹ predicted w/cm and actual w/cm contents of the mixtures. Overall, the Cementometerᵀᴹ device was found to precisely measure moisture levels in aggregates, but in concrete none of the modes were precise (all R² values were less than 0.065) nor accurate (p-value less than 0.044). On the other hand, the in-lab AASHTO microwave method produced statistically precise (R² of 0.62 or more) and accurate (p-value of 0.91) readings; and thus the in-lab AASHTO T318-02 method is recommended over the in-situ Cementometerᵀᴹ for w/cm ratio determination.

• Record URL:
  https://drive.google.com/file/d/1947QupGnI9tKzR4JFLLVCu0nJaCr4uvK/view?usp=sharing
• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/62255
• Corporate Authors:

  University of Utah

  Department of Civil and Environmental Engineering
  110 Central Campus Drive Suite 2000
  Salt Lake City, UT  United States  84112

  Utah Department of Transportation

  4501 South 2700 West
  Salt Lake City, UT  United States  84114-8410

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590

  U.S. Department of Transportation

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Allahham, Jafar
  • Bordelon, Amanda
• Publication Date: 2016-12

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 77p

Subject/Index Terms

• TRT Terms: Admixtures; Dielectric properties; Electrical resistivity; Microwave devices; Moisture meters; Statistical analysis; Water cement ratio
• Identifier Terms: American Association of State Highway and Transportation Officials; Cementometer
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 01717979
• Record Type: Publication
• Report/Paper Numbers: UT-16.21
• Contract Numbers: 16-8162
• Files: NTL, TRIS, ATRI, USDOT, STATEDOT
• Created Date: Sep 24 2019 2:53PM